1. Field
The present disclosure relates generally to communication systems, and more particularly, to H-ARQ timing for TDD relays.
2. Background
Wireless communication systems are widely used to provide a variety of communication services such as voice, data, broadcast, and others. These communication systems may be multiple-access systems supporting simultaneous resource use by multiple users. This resource sharing is accomplished through the use of shared system resources, including bandwidth and transmit power. A number of multiple access systems are currently in use and include code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), and orthogonal frequency division multiple access (OFDMA). These access systems may be used in conjunction with various communication standards such as those promulgated by 3GPP Long Term Evolution (3G LTE). LTE is an emerging telecommunication standard and is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology.
Wireless multiple access communication systems typically support multiple wireless terminals. Each wireless terminal, also known as a mobile device or user equipment (UE), communicates with one or more base stations using forward and reverse links. The forward link refers to communication link from the base stations to the mobile terminals or UEs, and may also be known as the downlink. The reverse link refers to the communication link from the UEs to the base stations (BS). The communication link may be established by a single link system or a multiple input, multiple output (MIMO) system.
The traffic generated by the UEs and BSs is managed in part by a serving network controller, which serves as the arbiter of wireless traffic. The network controller can send control information to UEs, assign wireless resources to UEs, manages uplink and downlink interference, and coordinates MIMO transmissions among neighboring BSs. The serving network controller acts as a central planner for managing the disparate wireless communications and ensures consistency and reliability.
As wireless networks and usage expand, network management becomes more complex. Networks must support both the latest generation of wireless devices from the moment of introduction, while maintaining support for older legacy equipment. Backward compatibility adds much design complexity to network planning and deployment. Changes to network standards have the potential to render millions of mobile phones, tablets, and computer accessories obsolete overnight. Backward compatibility ensures that the older legacy devices may be used with new standards that provide support for new devices and features.
Merely porting older standards into newer systems can lead to convoluted and inefficient system architectures, with rules applying based on equipment type and model. Such inefficiencies should be avoided by careful planning of the radio access network infrastructure (base stations, relay stations, repeater stations, and mobile switching controllers), core network infrastructure (location registers, billing and charging servers, subscription servers, and customer support infrastructure), and user equipment (mobile phones, personal digital assistants, and smart phones). Wireless communication standards groups such as 3GPP and 3GPP2 are charged with keeping backward compatibility in mind when new standards are adopted.
An example of backward compatibility issues involves the use of hybrid automatic repeat request (H-ARQ) when used in conjunction with a time division duplex (TDD) relay. There is a need in the art for a backward compatible downlink (DL) H-ARQ process and a backward compatible uplink (UL) H-ARQ process in the access link.